Effects of season and fertiliser rate on phosphorus concentrations in pasture and sheep faeces in hill country

The effects of different rates of superphosphate fertiliser (10, 20, 30, 50, and 100 kg/ha of P) and of slope (0 – 10, 11 – 20, 21 – 30, 31 – 40° and 41° +) on P concentrations in pasture were monitored on a seasonal basis for 3 years in hill country. Faecal P concentrations were also measured. Pasture P decreased with increasing slope. Pasture and faecal P concentrations increased with increasing fertiliser rate; both were highest in winter and spring and lowest in summer. A highly significant relationship ( r = 0.94) existed between the P concentration in pasture on offer for grazing within a paddock and P concentration of the faeces deposited subsequently during the grazing period. This close relationship will facilitate attempts to model P return via the grazing animal and to assess the effects on P losses by animal transfer.